用python3连oanda的模拟交易api时现HTTP Error 401: UNAUTHORIZED，新手求教:
import urllib.parse
import urllib.request

url = 'https://api-fxpractice.oanda....'
access_token = 'a554db3a48ac8180a6996a5547ba1663-ac5947e64456cc5842a34f4ce05e4380'
account_id = 'cawa11'
values = {'accountId':account_id}
headers = {'Authorization':'Bearer' access_token}

data = urllib.parse.urlencode(values).encode("utf-8")

req = urllib.request.Request(url, data, headers)
response = urllib.request.urlopen(req)
the_page = response.read()

报错：
Traceback (most recent call last):
File "C:UserslenovoDesktopbb.py", line 36, in <module>

response = urllib.request.urlopen(req)

File "C:Python34liburllibrequest.py", line 161, in urlopen

return opener.open(url, data, timeout)

File "C:Python34liburllibrequest.py", line 469, in open

response = meth(req, response)

File "C:Python34liburllibrequest.py", line 579, in http_response

'http', request, response, code, msg, hdrs)

File "C:Python34liburllibrequest.py", line 507, in error

return self._call_chain(*args)

File "C:Python34liburllibrequest.py", line 441, in _call_chain

result = func(*args)

File "C:Python34liburllibrequest.py", line 587, in http_error_default

raise HTTPError(req.full_url, code, msg, hdrs, fp)

urllib.error.HTTPError: HTTP Error 401: UNAUTHORIZED